1. Introduction

In this tutorial, we will learn how to switch between different themes dynamically on a web page. This feature will allow users to customize their view according to their preferences and improve their overall user experience.

By the end of this tutorial, you will be able to:

• Understand how to implement dynamic theme switching
• Apply JavaScript, CSS, and HTML to change themes
• Store user's theme preference and load it on subsequent visits

Prerequisites:

Basic understanding of HTML, CSS, and JavaScript is required to follow along with this tutorial.

2. Step-by-Step Guide

Concept Explanation

To implement dynamic theme switching, we need different CSS files for each theme. We'll use JavaScript to switch between these CSS files based on user input. We'll also use localStorage to store the user's theme preference and load it on subsequent visits.

Best Practices and Tips

• Keep CSS files organized and separate for each theme.
• Use meaningful names for CSS classes and id's.
• Use localStorage carefully, as it has a size limit.

3. Code Examples

Example 1: Basic Theme Switching

<!-- HTML -->
<div id="themeSwitcher">
    <button onclick="switchTheme('dark')">Dark Theme</button>
    <button onclick="switchTheme('light')">Light Theme</button>
</div>

/* CSS */
body.dark {
    background-color: black;
    color: white;
}
body.light {
    background-color: white;
    color: black;
}

// JavaScript
function switchTheme(theme) {
    document.body.className = theme;
}

In this example, we have two buttons that call the switchTheme function with a different argument. This function changes the className of the body element, which switches the theme.

Example 2: Storing Theme Preference

// JavaScript
function switchTheme(theme) {
    document.body.className = theme;
    localStorage.setItem('theme', theme);
}

window.onload = function() {
    var theme = localStorage.getItem('theme');
    if (theme) switchTheme(theme);
}

In this example, we use localStorage.setItem to store the user's theme preference. When the page loads, we use localStorage.getItem to retrieve the stored theme and apply it by calling switchTheme.

4. Summary

In this tutorial, we learned how to switch between different themes dynamically using JavaScript, CSS, and HTML. We also learned how to store the user's theme preference using localStorage and apply it on subsequent visits.

Next steps for learning would be to explore more about localStorage and how to create more complex themes using CSS.

Some additional resources are:

• MDN Web Docs: Using the Web Storage API
• W3Schools: JavaScript HTML DOM

5. Practice Exercises

Exercise 1: Create a webpage with 3 different themes and implement theme switching.

Exercise 2: Store the user's theme preference and apply it on subsequent visits.

Exercise 3: Add a feature to automatically switch to a 'night' theme based on the user's local time.

Solutions:

1. You can follow the code examples provided in this tutorial to create 3 different themes and implement theme switching.

2. Use localStorage.setItem to store the theme preference and localStorage.getItem to retrieve and apply it.

3. Use the Date object to get the current hour and switch to a 'night' theme if the hour is after 6 PM.

Tips for further practice: Try to create more complex themes and implement transition effects when switching themes.